Wet type friction plate

ABSTRACT

A wet friction plate is constructed such that a carbon based friction material is placed on an outer peripheral side of a friction plate and a paper based friction material is placed on an inside of a carbon based friction material. A transmission torque occupied by the paper based friction material is smaller than that occupied by the carbon based friction material. The wet friction plate can prevent a sudden unexpected slip at low temperature.

TECHNICAL FIELD

The present invention relates to a wet type friction plate used for a brake such as an electric chain block, an automatic transmission for an automobile and the like. More particularly, the present invention relates to a wet type friction plate equipped with a core plate in a disc shape and a friction member which is pasted and fixed at a predetermined interval in the circumferential direction of the core plate at a plurality of portions.

BACKGROUND ART

Conventionally, as a wet type friction plate used for a brake of an automatic transmission for an automobile, a wet type friction plate is equipped with a core plate in a disc shape and friction members are pasted and fixed at plural portions at a predetermined interval in the circumferential direction of the core plate. The plurality of the friction members uses two or more types of materials whose characteristics are different. (For example, see Patent Document 1).

The wet type friction plate above-mentioned is characterized in that it is higher in friction coefficient, the variation of the friction coefficient is smaller and is excellent in mechanical strength by changing the materials of the members of two types of friction plates when it is compared with a wet type friction plate on which one type of a friction member is alternately provided and fixed.

On the other hand, carbon fiber reinforced plastics (CFRP) are used as a friction member. In the case where the CFRP are used, there is a defect in that “chattering” or “grabbing chatter” is generated at the time when it is quickly stopped from the state where it is driven at low speed revolutions. Therefore, in order to resolve this defect, a friction plate in which “chattering” is prevented by alternately pasting a CFRP and a paper member at a predetermined interval at the same distance from the center of the core plate has been proposed. However, in the case of this friction plate, at a low temperature, it has a problem in that, for example, at the time when an electric chain block winds up a load slightly smaller than the load at which friction clutch works, and it winds down the load, a sudden, unexpected slip occurs.

-   Patent Document 1: Japanese Patent Application Laid-Open No.     2005-330989

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

As a result of studying the cause why a sudden, unexpected slip is generated at a low temperature, the inventor gained knowledge that because a paper member has a material characteristic where the material is hardened by lowering of the temperature, slip is generated at a lower temperature. The inventor also gained knowledge that even though a paper based friction member has a comparatively high friction force because an oil immersed into the friction boundary surface and pore section is solidified at a lower temperature, when the oil is melted by the friction heat, the friction force is rapidly lowered, and slip is generated.

An object of the present invention is to provide a wet type friction plate in which “chattering” is not generated and a sudden, unexpected slip does not occur at a lower temperature in a wet type friction plate using two types of a CFRP and a paper member having different characteristics as a friction member based on the knowledge described above.

Means for Solving Problem

In order to solve the problem, the present invention provides a wet type friction plate, comprising carbon based friction members that are divided into a plural number of members in a circumferential direction of a friction plate and a paper based friction member, the carbon based friction members and the paper based friction member being pasted and fixed at a predetermined interval. The carbon based friction members are provided on the circumferential side of the friction plate. The paper based friction member is provided on the inner side of it, and a transmission torque occupied by the paper based friction member is smaller than that occupied by the carbon based friction member.

The present invention also provides a wet type friction plate, wherein a ratio of moment arm r₁ of the paper based friction member with respect to a sum of the rΓ₁ and moment arm r₂ is in a range from 0.2 to 0.4.

The present invention further provides a wet type friction plate wherein a ratio of area occupied by the paper based friction member with respect to a sum of area of the paper based friction member and the carbon based friction member is in a range from 0.05 to 0.45.

Effects of the Invention

A wet type friction plate of the present invention has heat resistance (which a carbon based friction member has), fatigue resistance and a “chattering” generation prevention characteristic, (which a paper based friction member has), by providing a carbon based friction member on the circumferential side of the friction plate and providing a paper based friction member on the inner side of it. The wet type friction plate of the present invention can prevent the generation of a sudden, unexpected slip at a low temperature by making the transmission torque occupied by the paper based friction member smaller than that occupied by the carbon based friction member.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view of an electric chain block.

FIG. 2( a) is a cross sectional view of a friction clutch, and FIG. 2( b) is a partially enlarged view of it.

FIGS. 3( a)-(d) are plan views showing the respective modes in which friction members are pasted and fixed on a clutch plate.

FIG. 4 is a cross sectional view showing an aspect in which friction members are pasted and fixed on a clutch plate and rigger.

BEST MODE FOR CARRYING OUT THE INVENTION

A wet type friction plate of the present invention will be described with reference to the figures.

In the figures, reference numeral 1 denotes an electric chain block main body, reference numeral 2 denotes a motor containing section, reference numeral 3 denotes a motor output shaft, reference numeral 3 a denotes a pinion that is formed at the tip of the motor output shaft, reference numeral 4 denotes a load sheave, reference numeral 4 a denotes a boss section of the load sheave 4, reference numeral 5 denotes a load gear which spline- or serration-couples with the load sheave boss section 4 a, reference numeral 6 denotes a gear shaft having a gear 6 a whose one end is intermeshed with the load gear 5, reference numeral 7 denotes a clutch plate borne by bush 6 b of the gear shaft 6, reference numeral 7 a denotes a gear that is intermeshed with the pinion 3 a of the motor output shaft 3 and provided on the circumference of the clutch plate 7, reference numeral 8 denotes a rigger which presses on and contacts both sides of the clutch plate 7 and which is shaft-supported in a non-rotatable manner by the gear shaft 6, reference numeral 9 denotes a disc spring for biasing the rigger 8 to the sides of the clutch plate 7, reference numeral 10 denotes a disc spring presser, reference numeral 11 denotes a bearing of the gear shaft 6, reference numeral 12 denotes a nut for disc spring pressure control, and reference numeral 13 denotes a male screw. Reference numeral 14 denotes a speed reduction gear containing section, and reference numeral 15 denotes an electric equipment containing section for containing electric equipment 16. Reference numeral 17 denotes a CFRP based friction member which is pasted and fixed on the clutch plate or the rigger, and reference numeral 18 denotes a paper based friction member which is pasted and fixed on the clutch plate or the rigger.

According to the present embodiment, as shown in FIGS. 3 (a)-(d), the carbon based friction member 17, divided into the plural members, is pasted and fixed on the circumference of the clutch plate 7 in the circumferential direction, the divided or continuous paper based friction member 18 is pasted and fixed on the inner side of the clutch plate 7, and the transmission torque occupied by the paper friction member is smaller than that occupied by the carbon based friction member.

As shown in FIG. 3 (b), supposing the moment arm which is a distance from the center of the clutch plate 7 to the center of the paper based friction member 18 is r₁, and the moment arm which is a distance from the center of the clutch plate 7 to the center of the carbon based friction member 17 is r₂, then the ratio of the moment arm r₁ of the paper based friction member 18 and the sum of the moment arm r₁ and the moment arm r₂, which is a distance of the carbon based friction member 17, (hereinafter referred to as the ratio of the moment arm of the paper section) was obtained. A test was performed under a condition where the ratio of the moment arm of the paper section is in a range from 50% to 30%, and the most preferable range was checked.

Moreover, the ratio of the area which the paper based friction member occupies with respect to the sum of the area of the paper based friction member and the area of the carbon based friction member (hereinafter, referred to as the ratio of the paper section area) was obtained, and the most preferable range was checked.

The test results are indicated in Table 1.

In the table, the “slip setting value” is a minimum load at which the friction clutch has worked (slipped). Also, the value is represented with the magnification to the load rating, and is indicated using “W”.

Example: If the slip setting value is 1.7-fold of the load rating, the slip setting value is indicated as slip setting value being 1.7 W.

TABLE 1 Ratio of the moment Ratio of the Distance from the center of arm of the paper the gear 2 to the center of paper Area per section area the friction member section (%) friction member (%) (moment arm) mm paper/(carbon + segment (mm²) paper/(carbon + ID Nos. of Carbon Paper paper) × Carbon Paper paper) × Test result prototypes Models material material 100 material material 100 Cold test Chattering 81201 DS 42 42 50 441 441 50 NG (0.5 W) Good 101101 DS 42 35 45 441 305 41 NG (0.3 W) Good 101101-2 DS 42 31.75 43 441 152.5 26 NG (0.3 W) Good 101101-3 DS 42 30.5 42 441 94.3 18 NG (0.4 W) Good 10201 FS 57 39 41 993 615 38 NG (0.2 W) Good 10203 FS 57 43.5 43 993 305 23 NG (0.2 W) Good 10204 FS 57 39 41 993 307 24 NG (0.1 W) Good 10205 FS 57 34.5 38 993 310 24 Good (0.2 Good W) In Table 1, NG: Sudden, unexpected falling of the load occurred; Inside parenthesis: Increase of the slip setting value.

As clearly understood from the Table 1, in the Identification Nos. 10201, 10203, 10204 and 10205, the increase of the slip setting value is 0.2 W or less, the slip setting value satisfies the determination criteria; however, in the Identification Nos. 10201, 10203, and 10204, the falling of the load was generated by a sudden, unexpected slip. On the other hand, in the Identification No. 10205, the increased amount of the slip setting value satisfies the determination criteria, and the falling of the load was not generated. Since the ratio of the moment arm of the paper section in the Identification No. 10205 is 38% and the ratio of the moment arm of the Identification No. 10204 is 41%, it is estimated that the uppermost value of the ratio of the moment arm of the paper section is 40%.

Moreover, when the ratio of the moment arm of the paper section is decreased, the slip setting value is also decreased and the falling of the load is not generated; however, “chattering” is generated by decreasing the paper based friction member. The present inventor confirmed that “chattering” is generated when the ratio of the moment arm of the paper section becomes 20% or less.

Moreover, the present inventor confirmed that the ratio of the paper section area is most preferably in the range from 5% to 45%.

The present embodiment is explained as a mode in which a friction member is pasted and fixed on the clutch plate. However, as shown in FIG. 4 (b), the friction member may be pasted and fixed on the rigger. As shown in FIG. 4 (c), even in the case where the carbon based friction member is pasted and fixed on the clutch plate and even in the case where the paper based friction member is pasted and fixed on the rigger, the same effect as in the present embodiment is obtained.

Moreover, the present embodiment is explained as a mode in which the friction member is pasted and fixed on the clutch plate; however, it is capable of being applied to all of the wet type friction plate.

Since, with a wet type friction plate of the present invention, a sudden, unexpected slip is not generated at a lower temperature, a wet type friction plate of the present invention is particularly suitable for an electric chain block and a clutch of various types of transmissions and the like used at a lower temperature. 

What is claimed is:
 1. A wet type friction plate, comprising: a carbon based friction member divided into a plural number of carbon members in a circumferential direction of said friction plate and a paper based friction member, said carbon members and said paper based friction member being pasted and fixed on said friction plate, wherein said carbon members are provided on an outer side of said friction plate at a predetermined interval and said paper based friction member is provided on an inner side of said friction plate, wherein said paper based friction member has a moment arm r₁ which is a distance from a center of said friction plate to a center of said paper based friction member and said carbon based friction member has a moment arm r₂ which is a distance from said center of said friction plate to a center of said carbon based friction member, wherein a ratio of r₁ to a sum of r₁+r₂ is 0.38, and wherein a ratio of area occupied by said paper based friction member to a sum of areas occupied by said paper based friction member and said carbon based friction member is 0.24. 